Auto-gripping straps are an extremely widespread application in the manufacturing of clothing, or generally, in domestic applications.
Said straps consist of two parts. A first part comprising of the loops which are destined to cooperate, through a redundant hooking link, with a second part, for instance hooks, string-like elements with an over-sized head, analogue elements, etc.
For evident, cost-based reasons, particularly important when single-use articles are to be mass-produced, notably diapers, one has to research economical manufacturing processes.
An economical process known for garments, for instance in the form of bands, of the part comprising the loops of this type of strap, is the manufacturing of a laminate consisting of a chained or weft material with loops counter-glued on a support.
However, this process is relatively complex, in so far as it necessitates a separate preparation for each of the two external layers of the laminate, then a technically complex gluing operation.
The present invention therefore relates to the manufacturing process of a loop cloth, the steps of which are fewer and therefore simpler than those intervening in the manufacturing of a laminate.
A process of this type is put to use on a knitting machine, modified to produce a loop cloth, described in the American U.S. Pat. No. 4,003,222, published on Jan. 18, 1977.
The modification consists of the transformation of the fixed lancets system in a mobile system. The lateral movement of the lancets allows for high-speed hook manufacturing, with a very high degree of dimensional stability, over a knit framework.
The manufacturer of this machine, the German company LIBA MASCHINENFABRIK, had solved the problem of optimal control of the string in an original and efficient fashion.
It is also with a view to increase the speed and quality of production guides can be used on this machine type, as for instance on the knitting machine of the aforementioned company, described in the European patent application EP 511580, published on Nov. 4, 1992.
However, regardless of the quality of the product manufactured, the problems that arise from the mechanically fragile and dimensionally unstable structure of a knitted material remain.
Another known process consists of inserting loops in a sheet. The material this sheet is made of could feature all required characteristics, both in terms of resistance and flexibility.
Textile machinery that can operate this process is available on the market in different forms.
The main machine is manufactured by the company MALIMO. It produces stitched loops from a simple or double knit armor. The machine includes a gang of fixed lancets.
There also exist a few machines using hooks, which produce loops either as frames or stitched, by insertion on a sheet. In this case, the lancets are still fixed.
The fact that loops manufactured through these processes are flat on the surface of their support is a negative consequence of the fixedness of lancets. The ease of strapping complementary elements of the strap is therefore naturally decreased compared to the expected result of using perfectly straight loops.
The conclusion derived from the above review of the existing state of the process is that manufacturing processes that knit loops on a sheet are known, but there exist no simple and economical process that provides full satisfaction today. Particularly, loop cloth manufactured by those processes features neither the dimensional stability nor the structural characteristics required for heavy-duty applications, notably diapers.